Final answer:
The hold time for taco and tostada shells cannot be determined from the given options (5 seconds, 10 seconds, 15 seconds, or 20 seconds) without specific food service guidelines or additional context.
Step-by-step explanation:
The question regarding the hold time on taco and tostada shells seems to relate to food service guidelines or practices, which would fall under the category of Health or Food Safety. This question does not directly relate to any of the provided reference materials since those deal with energy content, incubation times, and examples of time addition, which are not relevant in determining the holding time of food items. Without specific food service industry guidelines or additional context, it is not possible to accurately determine the hold time for taco and tostada shells amongst the given options (5 seconds, 10 seconds, 15 seconds, or 20 seconds). Therefore, I cannot provide a definitive answer to this question.